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Metal material fatigue crack propagation prediction method

A technology of fatigue crack growth and crack growth, which is applied in the field of fatigue crack growth prediction of metal materials, can solve the problems of poor prediction accuracy, narrow practicability, and inability to predict crack growth, etc., and achieve the effect of expanding the scope of application and improving the prediction accuracy

Active Publication Date: 2017-12-22
AVIC BEIJING INST OF AERONAUTICAL MATERIALS
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Problems solved by technology

High-load hysteresis models are represented by Wheeler model and Willenborg model, which are characterized by simple calculation and convenient application, but they do not consider the closing effect of cracks, and the prediction accuracy is poor
The closure model is represented by the PREFFAS model, ONERA model and CORPUS model. The closure model makes some assumptions to reflect the influence of the closure effect on crack propagation, but the plastic deformation of the crack wake is not obtained through quantitative calculation, and the calculation accuracy is poor.
The strip yield model that describes the crack growth mechanism in the most detail is represented by the Newman model, which quantitatively calculates the effect of closure on crack growth on the basis of assuming that the crack plastic wake is a thin strip, and can only predict the crack growth under constant amplitude loading. Crack growth under variable amplitude loading cannot be predicted, and the practicability is narrow

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  • Metal material fatigue crack propagation prediction method
  • Metal material fatigue crack propagation prediction method
  • Metal material fatigue crack propagation prediction method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0032] In this example, 2024 aluminum alloy is selected, M(T) sample, thickness B=5mm, length L=160mm, width W=60mm, and the length of the prefabricated center crack is 6mm. The crack propagation tests were all carried out under the loading conditions of the Mini-TWIST load spectrum.

[0033] The residual stress field distribution equation near the crack tip under the variable amplitude load obtained by implementing steps 1 and 2 is as follows:

[0034]

[0035] Among them, a 1 is the yield strength of the material,

[0036] b 1 =0.02521×(R ol ) 2 +0.05176×R ol +14.96,

[0037] b 2 =0.2942×(R ol ) 2 -0.2842×R ol +15.26,

[0038] σ 1 =0.03769×(R ol )2 -0.006159×R ol +0.03644,

[0039] σ 2 =0.03384×(R ol ) 2 +0.03096×R ol +0.001621,

[0040] τ=σ 2 ×(R ol +3.999),

[0041]

[0042] According to the implementation steps 3 and 4, the crack growth prediction curve under this load spectrum is obtained, see image 3 , including the real test curve (indica...

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Abstract

The invention belongs to a metal material damage tolerance design technology and relates to a metal material fatigue crack propagation prediction method. The fatigue crack propagation prediction method comprises the following steps of determining residual stress strain field distribution near a crack tip in crack propagation; calculating a residual stress strength factor; determining a processing method for variable amplitude loading; and building a fatigue crack propagation model. According to the metal material fatigue crack propagation prediction method provided by the invention, the fatigue crack propagation prediction precision is improved; the application range is expanded; and the needs of modern airplane structure design are met.

Description

technical field [0001] The invention belongs to the metal material damage tolerance design technology, and relates to a metal material fatigue crack propagation prediction method. Background technique [0002] Modern aircraft structures use damage-tolerant designs to ensure flight safety. The aircraft is constantly subjected to alternating loads during actual use, so the analysis of fatigue crack growth under variable amplitude loads is the key to damage tolerance design. The commonly used crack propagation models in the world are mainly divided into three categories: high load hysteresis model, closed model and strip yield model. The high-load hysteresis model is represented by the Wheeler model and the Willenborg model, which are characterized by simple calculation and convenient application, but neither takes into account the crack closure effect, and the prediction accuracy is poor. The closed model is represented by the PREFFAS model, the ONERA model and the CORPUS mo...

Claims

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Application Information

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IPC IPC(8): G06F17/50G01N19/08
CPCG01N19/08G06F30/367
Inventor 张丽娜
Owner AVIC BEIJING INST OF AERONAUTICAL MATERIALS
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